Inbred maize line PHBG4

ABSTRACT

An inbred maize line, designated PHBG4, the plants and seeds of inbred maize line PHBG4, methods for producing a maize plant produced by crossing the inbred line PHBG4 with itself or with another maize plant, and hybrid maize seeds and plants produced by crossing the inbred line PHBG4 with another maize line or plant.

FIELD OF THE INVENTION

This invention is in the field of maize breeding, specifically relatingto an inbred maize line designated PHBG4.

BACKGROUND OF THE INVENTION

The goal of plant breeding is to combine in a single variety or hybridvarious desirable traits. For field crops, these traits may includeresistance to diseases and insects, tolerance to heat and drought,reducing the time to crop maturity, greater yield, and better agronomicquality. With mechanical harvesting of many crops, uniformity of plantcharacteristics such as germination and stand establishment, growthrate, maturity, and plant and ear height, is important.

Field crops are bred through techniques that take advantage of theplant's method of pollination. A plant is self-pollinated if pollen fromone flower is transferred to the same or another flower of the sameplant. A plant is cross-pollinated if the pollen comes from a flower ona different plant.

Plants that have been self-pollinated and selected for type for manygenerations become homozygous at almost all gene loci and produce auniform population of true breeding progeny. A cross between twodifferent homozygous lines produces a uniform population of hybridplants that may be heterozygous for many gene loci. A cross of twoplants each heterozygous at a number of gene loci will produce apopulation of hybrid plants that differ genetically and will not beuniform.

Maize plants (zea mays L.), often referred to as corn in the UnitedStates, can be bred by both self-pollination and cross-pollinationtechniques. Maize has separate male and female flowers on the sameplant, located on the tassel and the ear, respectively. Naturalpollination occurs in maize when wind blows pollen from the tassels tothe silks that protrude from the tops of the ears.

A reliable method of controlling male fertility in plants offers theopportunity for improved plant breeding. This is especially true fordevelopment of maize hybrids, that relies upon some sort of malesterility system. There are several options for controlling malefertility available to breeders, such as: manual or mechanicalemasculation (or detasseling), cytoplasmic male sterility, genetic malesterility, gametocides and the like.

Hybrid maize seed is typically produced by a male sterility systemincorporating manual or mechanical detasseling. Alternate strips of twoinbred varieties of maize are planted in a field, and the pollen-bearingtassels are removed from one of the inbreds (female). Providing thatthere is sufficient isolation from sources of foreign maize pollen, theears of the detasseled inbred will be fertilized only from the otherinbred (male), and the resulting seed is therefore hybrid and will formhybrid plants.

The laborious, and occasionally unreliable, detasseling process can beavoided by using cytoplasmic male-sterile (CMS) inbreds. Plants of a CMSinbred are male sterile as a result of factors resulting from thecytoplasmic, as opposed to the nuclear, genome. Thus, thischaracteristic is inherited exclusively through the female parent inmaize plants, since only the female provides cytoplasm to the fertilizedseed. CMS plants are fertilized with pollen from another inbred that isnot male-sterile. Pollen from the second inbred may or may notcontribute genes that make the hybrid plants male-fertile. Usually seedfrom detasseled fertile maize and CMS produced seed of the same hybridare blended to insure that adequate pollen loads are available forfertilization when the hybrid plants are grown.

There are several methods of conferring genetic male sterilityavailable, such as multiple mutant genes at separate locations withinthe genome that confer male sterility, as disclosed in U.S. Pat. Nos.4,654,465 and 4,727,219 to Brar et al. and chromosomal translocations asdescribed by Patterson in U.S. Pat. Nos. 3,861,709 and 3,710,511. Theseand all patents referred to are incorporated herein by reference. Inaddition to these methods, Albertsen et al., of Pioneer Hi-Bred, U.S.patent application No. 071848,433, have developed a system of nuclearmale sterility that includes: identifying a gene that is critical tomale fertility; silencing this native gene that is critical to malefertility; removing the native promoter from the essential malefertility gene and replacing it with an inducible promoter; insertingthis genetically engineered gene back into the plant; and thus creatinga plant that is male sterile because the inducible promoter is not "on"resulting in the male fertility gene not being transcribed. Fertility isrestored by inducing, or turning "on", the promoter, that in turn allowsthe gene that confers male fertility to be transcribed.

There are many other methods of conferring genetic male sterility in theart, each with it's own benefits and drawbacks. These methods use avariety of approaches such as delivering into the plant a gene encodinga cytotoxic substance associated with a male tissue specific promoter oran antisense system in which a gene critical to fertility is identifiedand an antisense to that gene is inserted in the plant (see:Fabinjanski, et al. EPO 89/3010153.8 publication no. 329,308 and PCTapplication PCT/CA90/00037 published as WO 90/08828).

Another system useful in controlling male sterility makes use ofgametocides. Gametocides are not a genetic system, but rather a topicalapplication of chemicals. These chemicals affect cells that are criticalto male fertility. The application of these chemicals affects fertilityin the plants only for the growing season in which the gametocide isapplied (see Carlson, Glenn R., U.S. Pat. No. 4,936,904). Application ofthe gametocide, timing of the application and genotype specificity oftenlimit the usefulness of the approach.

The use of male sterile inbreds is but one factor in the development ofmaize hybrids. The development of maize hybrids requires, in general,the development of homozygous inbred lines, the crossing of these lines,and the evaluation of the crosses. Pedigree breeding and recurrentselection breeding methods are used to develop inbred lines frombreeding populations. Breeding programs combine the genetic backgroundsfrom two or more inbred lines or various other broad-based sources intobreeding pools from that new inbred lines are developed by selfing andselection of desired phenotypes. The new inbreds are crossed with otherinbred lines and the hybrids from these crosses are evaluated todetermine which of those have commercial potential.

Pedigree breeding starts with the crossing of two genotypes, each ofthat may have one or more desirable characteristics that is lacking inthe other or that complement the other. If the two original parents donot provide all the desired characteristics, other sources can beincluded in the breeding population. In the pedigree method, superiorplants are selfed and selected in successive generations. In thesucceeding generations the heterozygous condition gives way tohomogeneous lines as a result of self-pollination and selection.Typically in the pedigree method of breeding five or more generations ofselfing and selection is practiced: F₁ →F₂ ; F₃ →F₄ ; F₄ →F₅, etc.

Recurrent selection breeding, backcrossing for example, can be used toimprove an inbred line. Backcrossing can be used to transfer a specificdesirable trait from one inbred or source to an inbred that lacks thattrait. This can be accomplished, for example, by first crossing asuperior inbred (recurrent parent) to a donor inbred (non-recurrentparent), that carries the appropriate gene(s) for the trait in question.The progeny of this cross is then mated back to the superior recurrentparent followed by selection in the resultant progeny for the desiredtrait to be transferred from the non-recurrent parent. After five ormore backcross generations with selection for the desired trait, theprogeny will be heterozygous for loci controlling the characteristicbeing transferred, but will be like the superior parent for most oralmost all other genes. The last backcross generation would be selfed togive pure breeding progeny for the gene(s) being transferred.

A single cross hybrid maize variety is the cross of two inbred lines,each of that has a genotype that complements the genotype of the other.The hybrid progeny of the first generation is designated F₁. In thedevelopment of hybrids only the F₁ hybrid plants are sought. PreferredF₁ hybrids are more vigorous than their inbred parents. This hybridvigor, or heterosis, can be manifested in many polygenic traits,including increased vegetative growth and increased yield.

The development of a hybrid maize variety involves three steps: (1) theselection of plants from various germplasm pools for initial breedingcrosses; (2) the selfing of the selected plants from the breedingcrosses for several generations to produce a series of inbred lines,that, although different from each other, breed true and are highlyuniform; and (3) crossing the selected inbred lines with differentinbred lines to produce the hybrid progeny (F₁). During the inbreedingprocess in maize, the vigor of the lines decreases. Vigor is restoredwhen two different inbred lines are crossed to produce the hybridprogeny (F₁). An important consequence of the homozygosity andhomogeneity of the inbred lines is that the hybrid between any twoinbreds will always be the same. Once the inbreds that give a superiorhybrid have been identified, the hybrid seed can be reproducedindefinitely as long as the homogeneity of the inbred parents ismaintained.

A single cross hybrid is produced when two inbred lines are crossed toproduce the F₁ progeny. A double cross hybrid is produced from fourinbred lines crossed in pairs (A×B and C×D) and then the two F₁ hybridsare crossed again (A×B)×(C×D). Much of the hybrid vigor exhibited by F₁hybrids is lost in the next generation (F₂). Consequently, seed fromhybrid varieties is not used for planting stock.

Maize is an important and valuable field crop. Thus, a continuing goalof plant breeders is to develop high-yielding maize hybrids that areagronomically sound based on stable inbred lines. The reasons for thisgoal are obvious: to maximize the amount of grain produced with theinputs used and minimize susceptibility of the crop to environmentalstresses. To accomplish this goal, the maize breeder must select anddevelop superior inbred parental lines for producing hybrids. Thisrequires identification and selection of genetically unique individualsthat occur in a segregating population. The segregating population isthe result of a combination of crossover events plus the independentassortment of specific combinations of alleles at many gene loci thatresults in specific genotypes. Based on the number of segregating genes,the frequency of occurrence of an individual with a specific genotypes.Based on the number of segregating genes, the frequency of occurrence ofan individual with a specific genotype is less than 1 in 10,000. Thus,even if the entire genotype of the parents has been characterized andthe desired genotype is known, only a few if any individuals having thedesired genotype may be found in a large F₂ or S₀ population. Typically,however, the genotype of neither the parents nor the desired genotype isknown in any detail.

In addition to the preceding problem, it is not known how the genotypewill react with the environment. This genotype by environmentinteraction is an important, yet unpredictable, factor in plantbreeding. A breeder of ordinary skill in the art cannot predict thegenotype, how that genotype will interact with various environments orthe resulting phenotypes of the developing lines, except perhaps in avery broad and general fashion. A breeder of ordinary skill in the artwould also be unable to recreate the same line twice from the very sameoriginal parents as the breeder is unable to direct how the genomescombine or how they will interact with the environmental conditions.This unpredictability results in the expenditure of large amounts ofresearch resources in the development of a superior new maize inbredline.

Pioneer research station staff propose about 400 to 500 new inbreds eachyear from over 2,000,000 pollinations. Of those proposed new inbreds,less than 50 and more commonly less than 30 are actually selected forcommercial use.

SUMMARY OF THE INVENTION

According to the invention, there is provided a novel inbred maize line,designated PHBG4. This invention thus relates to the seeds of inbredmaize line PHBG4, to the plants of inbred maize line PHBG4, and tomethods for producing a maize plant produced by crossing the inbred linePHBG4 with itself or another maize line. This invention further relatesto hybrid maize seeds and plants produced by crossing the inbred linePHBG4 with another maize line.

DEFINITIONS

In the description and examples that follow, a number of terms are usedherein. In order to provide a clear and consistent understanding of thespecification and claims, including the scope to be given such terms,the following definitions are provided. NOTE: ABS is in absolute termsand %MN is percent of the mean for the experiments in which the inbredor hybrid was grown. These designators will follow the descriptors todenote how the values are to be interpreted. Below are the descriptorsused in the data tables included herein.

ANT ROT=ANTHRACNOSE STALK ROT (Colletotrichum graminicola). A 1 to 9visual rating indicating the resistance to Anthracnose Stalk Rot. Ahigher score indicates a higher resistance.

BAR PLT=BARREN PLANTS. The percent of plants per plot that were notbarren (lack ears).

BRT STK=BRITTLE STALKS. This is a measure of the stalk breakage near thetime of pollination, and is an indication of whether a hybrid or inbredwould snap or break near the time of flowering under severe winds. Dataare presented as percentage of plants that did not snap.

BU ACR=YIELD (BUSHELS/ACRE). Yield of the grain at harvest in bushelsper acre adjusted to 15.5% moisture.

CLN=CORN LETHAL NECROSIS (synergistic interaction of maize chloroticmottle virus (MCMV) in combination with either maize dwarf mosaic virus(MDMV-A or MDMV-B) or wheat streak mosaic virus (WSMV)). A 1 to 9 visualrating indicating the resistance to Corn Lethal Necrosis. A higher scoreindicates a higher resistance.

COM RST=COMMON RUST (Puccinia sorghi). A 1 to 9 visual rating indicatingthe resistance to Common Rust. A higher score indicates a higherresistance.

DID=DRYDOWN. This represents the relative rate at which a hybrid willreach acceptable harvest moisture compared to other hybrids on a 1-9rating scale. A high score indicates a hybrid that dries relatively fastwhile a low score indicates a hybrid that dries slowly.

DIP ERS=DIPLODIA EAR MOLD SCORES (Diplodia maydis and Diplodiamacrospora). A 1 to 9 visual rating indicating the resistance toDiplodia Ear Mold. A higher score indicates a higher resistance.

DRP EAR=DROPPED EARS. A measure of the number of dropped ears per plotand represents the percentage of plants that did not drop ears prior toharvest.

D/T=DROUGHT TOLERANCE. This represents a 1-9 rating for droughttolerance, and is based on data obtained under stress conditions. A highscore indicates good drought tolerance and a low score indicates poordrought tolerance.

EAR HT=EAR HEIGHT. The ear height is a measure from the ground to thehighest placed developed ear node attachment and is measured in inches.

EAR MLD=General Ear Mold. Visual rating (1-9 score) where a "1" is verysusceptible and a "9" is very resistant. This is based on overall ratingfor ear mold of mature ears without determining the specific moldorganism, and may not be predictive for a specific ear mold.

EAR SZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher therating the larger the ear size.

ECB 1LF=EUROPEAN CORN BORER FIRST GENERATION LEAF FEEDING (Ostrinianubilalis). A 1 to 9 visual rating indicating the resistance topreflowering leaf feeding by first generation European Corn Borer. Ahigher score indicates a higher resistance.

ECB 2IT=EUROPEAN CORN BORER SECOND GENERATION INCHES OF TUNNELING(Ostrinia nubilalis). Average inches of tunneling per plant in thestalk.

ECB 2SC=EUROPEAN CORN BORER SECOND GENERATION (Ostrinia nubilalis). A 1to 9 visual rating indicating post flowering degree of stalk breakageand other evidence of feeding by European Corn Borer, Second Generation.A higher score indicates a higher resistance.

ECB DPE=EUROPEAN CORN BORER DROPPED EARS (Ostrinia nubilalis). Droppedears due to European Corn Borer. Percentage of plants that did not dropears under second generation corn borer infestation.

EST CNT=EARLY STAND COUNT. This is a measure of the stand establishmentin the spring and represents the number of plants that emerge on perplot basis for the inbred or hybrid.

EYE SPT=Eye Spot (Kabatiella zeae or Aureobasidium zeae). A 1 to 9visual rating indicating the resistance to Eye Spot. A higher scoreindicates a higher resistance.

FUS ERS=FUSARIUM EAR ROT SCORE (Fusarium moniliforme or Fusariumsubglutinans). A 1 to 9 visual rating indicating the resistance toFusarium ear rot. A higher score indicates a higher resistance.

GDU=Growing Degree Units. Using the Barger Heat Unit Theory, thatassumes that maize growth occurs in the temperature range 50° F.-86° F.and that temperatures outside this range slow down growth; the maximumdaily heat unit accumulation is 36 and the minimum daily heat unitaccumulation is 0. The seasonal accumulation of GDU is a major factor indetermining maturity zones.

GDU SHD=GDU TO SHED. The number of growing degree units (GDUs) or heatunits required for an inbred line or hybrid to have approximately 50percent of the plants shedding pollen and is measured from the time ofplanting. Growing degree units are calculated by the Barger Method,where the heat units for a 24-hour period are: ##EQU1##

The highest maximum temperature used is 86° F. and the lowest minimumtemperature used is 50° F. For each inbred or hybrid it takes a certainnumber of GDUs to reach various stages of plant development.

GDU SLK=GDU TO SILK. The number of growing degree units required for aninbred line or hybrid to have approximately 50 percent of the plantswith silk emergence from time of planting. Growing degree units arecalculated by the Barger Method as given in GDU SHD definition.

GIB ERS=GIBBERELLA EAR ROT (PINK MOLD) (Gibberella zeae). A 1 to 9visual rating indicating the resistance to Gibberella Ear Rot. A higherscore indicates a higher resistance.

GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis). A 1 to 9 visual ratingindicating the resistance to Gray Leaf Spot. A higher score indicates ahigher resistance.

GOS WLT=Goss' Wilt (Corynebacterium nebraskense). A 1 to 9 visual ratingindicating the resistance to Goss' Wilt. A higher score indicates ahigher resistance.

GRN APP=GRAIN APPEARANCE. This is a 1 to 9 rating for the generalappearance of the shelled grain as it is harvested based on such factorsas the color of harvested grain, any mold on the grain, and any crackedgrain. High scores indicate good grain quality.

H/POP=YIELD AT HIGH DENSITY. Yield ability at relatively high plantdensities on 1-9 relative rating system with a higher number indicatingthe hybrid responds well to high plant densities for yield relative toother hybrids. A 1, 5, and 9 would represent very poor, average, andvery good yield response, respectively, to increased plant density.

HC BLT=HELMINTHOSPORIUM CARBONUM LEAF BLIGHT (Helminthosporiumcarbonum). A, 1 to 9 visual rating indicating the resistance toHelminthosporium infection. A higher score indicates a higherresistance.

HD SMT=HEAD SMUT (Sphacelotheca reiliana). This score indicates thepercentage of plants not infected.

INC D/A,=GROSS INCOME (DOLLARS PER ACRE). Relative income per acreassuming drying costs of two cents per point above 15.5 percent harvestmoisture and current market price per bushel.

INCOME/ACRE. Income advantage of hybrid to be patented over other hybridon per acre basis.

INC ADV=GROSS INCOME ADVANTAGE. GROSS INCOME advantage of variety #1over variety #2.

L/POP=YIELD AT LOW DENSITY. Yield ability at relatively low plantdensities on a 1-9 relative system with a higher number indicating thehybrid responds well to low plant densities for yield relative to otherhybrids. A 1, 5, and 9 would represent very poor, average, and very goodyield response, respectively, to low plant density.

MDM CPX=MAIZE DWARF MOSAIC COMPLEX (MDMV=Maize Dwarf Mosaic Virus andMCDV=Maize Chlorotic Dwarf Virus). A, 1 to 9 visual rating indicatingthe resistance to Maize Dwarf Mosaic Complex. A, higher score indicatesa higher resistance.

MST=HARVEST MOISTURE. The moisture is the actual percentage moisture ofthe grain at harvest.

MST ADV=MOISTURE ADVANTAGE. The moisture advantage of variety #1 overvariety #2 as calculated by: MOISTURE of variety #2--MOISTURE of variety#1=MOISTURE ADVANTAGE of variety #1.

NLF BLT=Northern Leaf Blight (Helminthosporium turcicum or Exserohilumturcicum). A 1 to 9 visual rating indicating the resistance to NorthernLeaf Blight. A higher score indicates a higher resistance.

PLT HT=PLANT HEIGHT. This is a measure of the height of the plant fromthe ground to the tip of the tassel in inches.

POL SC=POLLEN SCORE. A 1 to 9 visual rating indicating the amount ofpollen shed. The higher the score the more pollen shed.

POL WT=POLLEN WEIGHT. This is calculated by dry weight of tasselscollected as shedding commences minus dry weight from similar tasselsharvested after shedding is complete.

It should be understood that the inbred can, through routinemanipulation of cytoplasmic or other factors, be produced in amale-sterile form.

POP K/A=PLANT POPULATIONS. Measured as 1000s per acre.

POP ADV=PLANT POPULATION ADVANTAGE. The plant population advantage ofvariety #1 over variety #2 as calculated by PLANT POPULATION of variety#2--PLANT POPULATION of variety #1=PLANT POPULATION ADVANTAGE of variety#1.

PRM=PREDICTED Relative Maturity. This trait, predicted relativematurity, is based on the harvest moisture of the grain. The relativematurity rating is based on a known set of checks and utilizes standardlinear regression analyses and is referred to as the ComparativeRelative Maturity Rating System that is similar to the MinnesotaRelative Maturity Rating System.

PRM SHD=A relative measure of the growing degree units (GDU) required toreach 50% pollen shed. Relative values are predicted values from thelinear regression of observed GDU's on relative maturity of commercialchecks.

RT LDG=ROOT LODGING. Root lodging is the percentage of plants that donot root lodge; plants that lean from the vertical axis as anapproximately 30° angle or greater would be counted as root lodged.

RTL ADV=ROOT LODGING ADVANTAGE. The root lodging advantage of variety #1over variety #2.

SCT GRN=SCATTER GRAIN. A 1 to 9 visual rating indicating the amount ofscatter grain (lack of pollination or kernel abortion) on the ear. Thehigher the score the less scatter grain.

SDG VGR=SEEDLING VIGOR. This is the visual rating (1 to 9) of the amountof vegetative growth after emergence at the seedling stage(approximately five leaves). A higher score indicates better vigor.

SEL IND=SELECTION INDEX. The selection index gives a single measure ofthe hybrid's worth based on information for up to five traits. A maizebreeder may utilize his or her own set of traits for the selectionindex. One of the traits that is almost always included is yield. Theselection index data presented in the tables represent the mean valueaveraged across testing stations.

SLF BLT=SOUTHERN LEAF BLIGHT (Helminthosporium maydis or Bipolarismaydis). A 1 to 9 visual rating indicating the resistance to SouthernLeaf Blight. A higher score indicates a higher resistance.

SOU RST=SOUTHERN RUST (Puccinia polysora). A 1 to 9 visual ratingindicating the resistance to Southern Rust. A higher score indicates ahigher resistance.

STA GRN=STAY GREEN. Stay green is the measure of plant health near thetime of black layer formation (physiological maturity). A high scoreindicates better late-season plant health.

STD ADV=STALK STANDING ADVANTAGE. The advantage of variety #1 overvariety #2 for the trait STK CNT.

STK CNT=NUMBER OF PLANTS. This is the final stand or number of plantsper plot.

STK LDG=STALK LODGING. This is the percentage of plants that did notstalk lodge (stalk breakage) as measured by either natural lodging orpushing the stalks and determining the percentage of plants that breakbelow the ear.

STW WLT=Stewart's Wilt (Erwinia stewartii). A 1 to 9 visual ratingindicating the resistance to Stewart's Wilt. A higher score indicates ahigher resistance.

TAS BLS=TASSEL BLAST. A 1 to 9 visual rating was used to measure thedegree of blasting (necrosis due to heat stress) of the tassel at thetime of flowering. A 1 would indicate a very high level of blasting attime of flowering, while a 9 would have no tassel blasting.

TAS SZ=TASSEL SIZE. A 1 to 9 visual rating was used to indicate therelative size of the tassel. The higher the rating the larger thetassel.

TAS WT=TASSEL WEIGHT. This is the average weight of a tassel (grams)just prior to pollen shed.

TEX EAR=EAR TEXTURE. A 1 to 9 visual rating was used to indicate therelative hardness (smoothness of crown) of mature grain. A 1 would bevery soft (extreme dent) while a 9 would be very hard (flinty or verysmooth crown).

TILLER=TILLERS. A count of the number of tillers per plot that couldpossibly shed pollen was taken. Data is given as a percentage oftillers: number of tillers per plot divided by number of plants perplot.

TST WT=TEST WEIGHT (UNADJUSTED). The measure of the weight of the grainin pounds for a given volume (bushel).

TST WTA=TEST WEIGHT ADJUSTED. The measure of the weight of the grain inpounds for a given volume (bushel) adjusted for 15.5 percent moisture.

TSW ADV=TEST WEIGHT ADVANTAGE. The test weight advantage of variety #1over variety #2.

WIN M%=PERCENT MOISTURE WINS.

WIN Y%=PERCENT YIELD WINS.

YLD=YIELD. It is the same as BU ACR ABS.

YLD ADV=YIELD ADVANTAGE. The yield advantage of variety #1 over variety#2 as calculated by: YIELD of variety #1--YIELD variety #2=yieldadvantage of variety #1.

YLD SC=YIELD SCORE. A 1 to 9 visual rating was used to give a relativerating for yield based on plot ear piles. The higher the rating thegreater visual yield appearance.

DETAILED DESCRIPTION OF THE INVENTION

Inbred maize lines are typically developed for use in the production ofhybrid maize lines. Inbred maize lines need to be highly homogeneous,homozygous and reproducible to be useful as parents of commercialhybrids. There are many analytical methods available to determine thehomozygotic and phenotypic stability of these inbred lines.

The oldest and most traditional method of analysis is the observation ofphenotypic traits. The data is usually collected in field experimentsover the life of the maize plants to be examined. Phenotypiccharacteristics most often observed are for traits associated with plantmorphology, ear and kernel morphology, insect and disease resistance,maturity, and yield.

In addition to phenotypic observations, the genotype of a plant can alsobe examined. There are many laboratory-based techniques available forthe analysis, comparison and characterization of plant genotype; amongthese are Isozyme Electrophoresis, Restriction Fragment LengthPolymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs),Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA AmplificationFingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs),Amplified Fragment Length Polymorphisms (AFLPs), and Simple SequenceRepeats (SSRs) which are also referred to as Microsatellites.

The most widely used of these laboratory techniques are IsozymeElectrophoresis and RFLPs as discussed in Lee, M., "Inbred Lines ofMaize and Their Molecular Markers," The Maize Handbook,(Springer-Verlag, New York, Inc. 1994, at 423-432) incorporated hereinby reference. Isozyme Electrophoresis is a useful tool in determininggenetic composition, although it has relatively low number of availablemarkers and the low number of allelic variants among maize inbreds.RFLPs have the advantage of revealing an exceptionally high degree ofallelic variation in maize and the number of available markers is almostlimitless.

Maize RFLP linkage maps have been rapidly constructed and widelyimplemented in genetic studies. One such study is described inBoppenmaier, et al., "Comparisons among strains of inbreds for RFLPs",Maize Genetics Cooperative Newsletter, 65:1991, pg. 90, is incorporatedherein by reference. This study used 101 RFLP markers to analyze thepatterns of 2 to 3 different deposits each of five different inbredlines. The inbred lines had been selfed from 9 to 12 times before beingadopted into 2 to 3 different breeding programs. It was results fromthese 2 to 3 different breeding programs that supplied the differentdeposits for analysis. These five lines were maintained in the separatebreeding programs by selfing or sibbing and rogueing off-type plants foran additional one to eight generations. After the RFLP analysis wascompleted, it was determined the five lines showed 0-2% residualheterozygosity. Although this was a relatively small study, it can beseen using RFLPs that the lines had been highly homozygous prior to theseparate strain maintenance.

PHBG4 produces hybrids that are high yielding and short in stature. Theinbred has very good staygreen and has above average brittle stalkresistance.

Inbred maize line PHBG4 is a yellow, dent maize inbred that provides anacceptable male parental line in crosses for producing first generationF 1 maize hybrids. PHBG4 is adapted to the Southwest region of theUnited States.

The inbred has shown uniformity and stability within the limits ofenvironmental influence for all the traits as described in the VarietyDescription Information (Table 1 ) that follows. Most of the data in theVariety Description information was collected at Johnston, Iowa. Theinbred has been self-pollinated and ear-rowed a sufficient number ofgenerations with careful attention paid to uniformity of plant type toensure the homozygousity and phenotypic stability necessary to use incommercial production. The line has been increased both by hand and inisolated fields with continued observation for uniformity. No varianttraits have been observed or are expected in PHBG4.

Inbred maize line PHBG4, being substantially homozygous, can bereproduced by planting seeds of the line, growing the resulting maizeplants under self-pollinating or sib-pollinating conditions withadequate isolation, and harvesting the resulting seed, using techniquesfamiliar to the agricultural arts.

                  TABLE 1                                                         ______________________________________                                        VARIETY DESCRIPTION INFORMATION                                               INBRED = PHBG4                                                                ______________________________________                                        Type: Dent       Region Best Adapted: Southwest                               A.  Maturity: Average across maturity zones. Zone: 0                              GDU Shed: 1560                                                                GDU Silk: 1570                                                                No. Reps: 34                                                              B.  Plant Characteristics:                                                        Plant height (to tassel tip): 232 cm                                          Length of top ear internode: 17 cm                                            Number of ears per stalk: Slight, two ear tendency                            Ear height (to base of top ear): 86 cm                                        Number of tillers: 1-2                                                        Cytoplasm type: Normal                                                    C.  Leaf:                                                                         Color: (B14) Dark Green*                                                      Angle from Stalk: <30 degrees                                                 Marginal Waves: (WF9) Few                                                     Number of Leaves (mature plants): 21                                          Sheath Pubescence: (W22) Light                                                Longitudinal Creases: (OH56A) Few                                             Length (Ear node leaf): 87 cm                                                 Width (widest point, ear node leaf): 9 cm                                 D.  Tassel:                                                                       Number lateral branches: 7                                                    Branch Angle from central spike: <30 degrees                                  Pollen Shed: (KY21) Heavy based on Pollen Yield                               Test (128% of experiment means)                                               Peduncle Length (top leaf to basal branches): 17 cm                           Anther Color: Red*                                                            Glume Color: Green*                                                       E.  Ear (Husked Ear Data Except When Stated Otherwise):                           Length: 17 cm                                                                 Weight: 106 gm                                                                Mid-point Diameter: 40 mm                                                     Silk Color: Pink*                                                             Husk Extension (Harvest stage): Medium                                        (barely covering ear)                                                         Husk Leaf: Short (<8 cm)                                                      Taper of Ear: Average                                                         Position of Shank (dry husks): Horizontal                                     Kernel Rows: Straight, distinct Number 16                                     Husk Color (fresh): Light Green*                                              Husk Color (dry): Buff*                                                       Shank Length: 8 cm                                                            Shank (No. of internodes): 8                                              F.  Kernel (Dried):                                                               Size (from ear mid-point)                                                     Length: 10 mm                                                                 Width: 8 mm                                                                   Thick: 5 mm                                                                   Shape Grade (% rounds): (% medium round based on                              Parent Test Data)                                                             Pericarp Color: Colorless*                                                    Aleurone Color: Homozygous Yellow*                                            Endosperm Color: Yellow*                                                      Endosperm Type: Normal Starch                                                 Gm Wt/100 Seeds (unsized): 25 gm                                          G.  Cob:                                                                          Diameter at mid-point: 27 mm                                                  Strength: Strong                                                              Color: Red*                                                               H.  Diseases:                                                                     Corn Lethal Necrosis (MCMV = Maize                                            Chlorotic Mottle Virus and                                                    MDMV = Maize Dwarf Mosaic Virus): Susceptible                                 Anthracnose Stalk Rot (C. graminicola): Intermediate                          S. Leaf Blight (B. maydis): Intermediate                                      N. Leaf Blight (E. turcicum): Intermediate                                    Common Rust (P. sorghi): Intermediate                                         Gray Leaf Spot (C. zeae): Intermediate                                        Stewart's Wilt (E. stewartii): Resistant                                      Head Smut (S. reiliana): Susceptible                                          Fusarium Ear Mold (F. moniliforme): Intermediate                          I.  Insects:                                                                      European Corn Borer-1 Leaf Damage (Preflowering):                             Resistant                                                                     European Corn Borer-2 (Post-flowering): Susceptible                           The above descriptions are based on a scale of 1-9, 1                         being highly susceptible, 9 being highly resistant.                           S (Susceptible): Would generally represent a score of 1-3.                    I (Intermediate): Would generally represent a score of 4-5.                   R (Resistant): Would generally represent a score of 6-7.                      H (Highly Resistant): Would generally represent a                             score of 8-9. Highly resistant does not imply                                 the inbred is immune.                                                     J.  Variety Most Closely Resembling:                                          Character    Inbred                                                           Maturity     PHR03                                                            Usage        PHR03                                                            ______________________________________                                         *In interpreting the foregoing color designations, reference may be had t     the Munsell Glossy Book of Color, a standard color reference.                 Data for Items B, C, D, E, F, and G is based primarily on a maximum of        four reps from Johnston, Iowa grown in 1994. and 1994, plus description       information from the maintaining station.                                     PHR03 (PVP Certificate No. 9100097) is a Pioneer HiBred International,        Inc. proprietary inbred.                                                 

ELECTROPHORESIS RESULTS

Isozyme Genotypes for PHBG4

Isozyme data were generated for inbred maize line PHBG4 according to theprocedures described in Stuber, C. W., Wendel, J. F., Goodman, M. M.,and Smith, J. S. C., "Techniques and Scoring Procedures for Starch GelElectrophoresis of Enzymes from Maize (Zea mays L.)", Technical BulletinNo. 286, North Carolina Agricultural Research Service, North CarolinaState University, Raleigh, N.C. (1988).

The data in Table 2 compares PHBG4 with its parents, PHR63 and PHR03.

                  TABLE 2                                                         ______________________________________                                        ELECTROPHORESIS RESULTS FOR PHBG4                                             AND ITS PARENTS PHR63 AND PHR03                                                      PARENTS                                                                LOCI     PHBG4         PHR63   PHR03                                          ______________________________________                                        ACP1     4             4       4                                              ADH1     4             4       4                                              CAT3     9             9       9                                              DIA1     8             8       8                                              GOT1     4             4       4                                              GOT2     4             2       4                                              GOT3     4             4       4                                              IDH1     4             4       4                                              IDH2     6             6       6                                              MDH1     6             6       6                                              MDH2     6             6       3.5                                            MDH3     16            16      16                                             MDH4     12            12      12                                             MDH5     12            12      12                                             MMM      4             4       4                                              PGM1     9             9       9                                              PGM2     4             4       3                                              PGD1     3.8           3.8     3.8                                            PGD2     5             5       5                                              PHI1     4             4       4                                              ______________________________________                                    

INDUSTRIAL APPLICABILITY

This invention also is directed to methods for producing a maize plantby crossing a first parent maize plant with a second parent maize plantwherein the first or second parent maize plant is an inbred maize plantfrom the line PHBG4. Further, both first and second parent maize plantscan come from the inbred maize line PHBG4. Thus, any such methods usingthe inbred maize line PHBG4 are part of this invention: selfing,backcrosses, hybrid production, crosses to populations, and the like.All plants produced using inbred maize line PHBG4 as a parent are withinthe scope of this invention. Advantageously, the inbred maize line isused in crosses with other, different, maize inbreds to produce firstgeneration (F₁) maize hybrid seeds and plants with superiorcharacteristics.

As used herein, the term plant includes plant cells, plant protoplasts,plant cell tissue cultures from which maize plants can be regenerated,plant calli, plant clumps, and plant cells that are intact in plants orparts of plants, such as embryos, pollen, flowers, kernels, ears, cobs,leaves, husks, stalks, roots, root tips, anthers, silk and the like.

Duncan, Williams, Zehr, and Widholm, Planta (1985) 165:322-332 reflectsthat 97% of the plants cultured that produced callus were capable ofplant regeneration. Subsequent experiments with both inbreds and hybridsproduced 91% regenerable callus that produced plants. In a further studyin 1988, Songstad, Duncan & Widholm in Plant Cell Reports (1988),7:262-265 reports several media additions that enhance regenerability ofcallus of two inbred lines. Other published reports also indicated that"nontraditional" tissues are capable of producing somatic embryogenesisand plant regeneration. K. P. Rao, et al., Maize Genetics CooperationNewsletter, 60:64-65 (1986), refers to somatic embryogenesis from glumecallus cultures and B. V. Conger, et al., Plant Cell Reports, 6:345-347(1987) indicates somatic embryogenesis from the tissue cultures of maizeleaf segments. Thus, it is clear from the literature that the state ofthe art is such that these methods of obtaining plants are, and were,"conventional" in the sense that they are routinely used and have a veryhigh rate of success.

Tissue culture of maize is described in European Patent Application,publication 160,390, incorporated herein by reference. Maize tissueculture procedures are also described in Green and Rhodes, "PlantRegeneration in Tissue Culture of Maize," Maize for Biological Research(Plant Molecular Biology Association, Charlottesville, Va. 1982, at367-372) and in Duncan, et al., "The Production of Callus Capable ofPlant Regeneration from Immature Embryos of Numerous Zea MaysGenotypes," 165 Planta 322-332 (1985). Thus, another aspect of thisinvention is to provide cells which upon growth and differentiationproduce maize plants having the physiological and morphologicalcharacteristics of inbred line PHBG4.

Maize is used as human food, livestock feed, and as raw material inindustry. The food uses of maize, in addition to human consumption ofmaize is kernels, include both products of dry- and wet-millingindustries. The principal products of maize dry milling are grits, mealand flour. The maize wet-milling industry can provide maize starch,maize syrups, and dextrose for food use. Maize oil is recovered frommaize germ, that is a by-product of both dry- and wet-millingindustries.

Maize, including both grain and non-grain portions of the plant, is alsoused extensively as livestock feed, primarily for beef cattle, dairycattle, hogs, and poultry.

Industrial uses of maize include production of ethanol, maize starch inthe wet-milling industry and maize flour in the dry-milling industry.The industrial applications of maize starch and flour are based onfunctional properties, such as viscosity, film formation, adhesiveproperties, and ability to suspend particles. The maize starch and flourhave application in the paper and textile industries. Other industrialuses include applications in adhesives, building materials, foundrybinders, laundry starches, explosives, oil-well muds, and other miningapplications.

Plant parts other than the grain of maize are also used in industry: forexample, stalks and husks are made into paper and wallboard and cobs areused for fuel and to make charcoal.

The seed of inbred maize line PHBG4, the plant produced from the inbredseed, the hybrid maize plant produced from the crossing of the inbred,hybrid seed, and various parts of the hybrid maize plant can be utilizedfor human food, livestock feed, and as a raw material in industry.

PERFORMANCE EXAMPLES OF PHBG4

In the examples that follow, the traits and characteristics of inbredmaize line PHBG4 are given as a line in comparison with other inbredsand in hybrid combination. The data collected on inbred maize line PHBG4is presented for the key characteristics and traits.

Table 3A compares PHBG4 to its PHR63 parent. PHBG4 is higher yieldingthan PHR63. PHBG4 has better staygreen and a higher early stand countcompared to PHR63. PHBG4 is a taller inbred with higher ear placementand sheds (GDU shed) later than PHR63.

Table 3B compares PHBG4 to its PHR03 parent. The data shows PHBG4 ishigher yielding, though not significant, and has a significantly highergrain harvest moisture than PHR03. PHBG4 is shorter with lower earplacement and sheds (GDU shed)later than PHR03.

Table 4 compares PHBG4 to PHR03 when they were crossed to the sameinbreds and grown in the same experiments. The PHBG4 hybrids haveslightly lower yield but higher grain harvest moisture than the PHRO3hybrids. The PHBG4 hybrids are shorter with lower ear placement comparedto the PHR03 hybrids. The PHBG4 hybrids have better stalk and rootlodging resistance, staygreen and seedling vigor compared to the PHRO3hybrids.

                                      TABLE 3A                                    __________________________________________________________________________    PAIRED INBRED COMPARISON DATA                                                 VARIETY #1 = PHBG4                                                            VARIETY #2 = PHR63                                                            __________________________________________________________________________                BU   BU       STK  RT  STA  TST                                           VAR ACR  ACR  MST LDG  LDG GRN  WrA                                           #   ABS  % MN % MN                                                                              % MN % MN                                                                              % MN % MN                                  __________________________________________________________________________    TOTAL SUM                                                                             1   56.3 150  109 84   122 120  102                                           2   36.5 90   108 87   104 96   98                                            LOCS                                                                              3    3    3   3     1  19   3                                             REPS                                                                              5    5    5   5     1  22   5                                             DIFF                                                                              19.8 60   1   3     17 23   4                                             PROB                                                                              .015+                                                                              .076*                                                                              .774                                                                              .674     .036+                                                                              .174                                  __________________________________________________________________________                SDG EST  STK PLT  EAR  BRT GDU                                            VAR VGR CNT  CNT HT   HT   STK SHD                                            #   % MN                                                                              % MN % MN                                                                              % MN % MN % MN                                                                              % MN                                   __________________________________________________________________________    TOTAL SUM                                                                             1   97  107  103 104  102  106 105                                            2   101 102  103 96   89   106 98                                             LOCS                                                                              35  62   45  21   21   14  52                                             REPS                                                                              41  116  60  25   25   16  65                                             DIFF                                                                              4   5    0   8    13   0   7                                              PROB                                                                              .439                                                                              .014+                                                                              .995                                                                              .000#                                                                              .003#                                                                              .718                                                                              .000#                                  __________________________________________________________________________     * = 10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

                                      TABLE 3B                                    __________________________________________________________________________    PAIRED INBRED COMPARISON DATA                                                 VARIETY #1 = PHBG4                                                            VARIETY #2 = PHR03                                                            __________________________________________________________________________                    BU  BU       STK RT  STA TST                                          VAR PRM ACR ACR MST  LDG LDG GRN WTA                                          #   SHD ABS % MN                                                                              % MN % MN                                                                              % MN                                                                              % MN                                                                              % MN                                 __________________________________________________________________________    TOTAL SUM                                                                             1   116 61.4                                                                              138 113  84  90  115 102                                          2   116 54.8                                                                              111 106  96  95  110 100                                          LOCS                                                                              1   5   5   5    3   2   24  3                                            REPS                                                                              1   9   9   9    5   3   30  5                                            DIFF                                                                              0   6.6 28  7    12  6   5   2                                            PROB    .359                                                                              .286                                                                              .052*                                                                              .350                                                                              .500                                                                              .470                                                                              .345                                 __________________________________________________________________________                SDG  EST STK  PLT  EAR  BRT GDU                                           VAR VGR  CNT CNT  HT   HT   STK SHD                                           #   % MN % MN                                                                              % MN % MN % MN % MN                                                                              % MN                                  __________________________________________________________________________    TOTAL SUM                                                                             1   96   107 103  103  101  108 105                                           2   104  108 107  106  112  109 104                                           LOCS                                                                              55   95  84   28   27   17  70                                            REPS                                                                              72   167 124  36   34   22  91                                            DIFF                                                                              8    1   3    3    10   1   1                                             PROB                                                                              .053*                                                                              .604                                                                              .052*                                                                              .020+                                                                              .001#                                                                              .110                                                                              .023+                                 __________________________________________________________________________     * = 10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

                                      TABLE 4                                     __________________________________________________________________________    Average Inbred By Tester Performance Comparing PHBG4 to PHR03 Crossed To      The Same                                                                      Inbred Testers And Grown In The Same Experiments. All Values Are              Expressed As Percent Of                                                       The Experiment Mean Except Predicted RM, Selection Index, and Yield           (BU/ACR)                                                                      __________________________________________________________________________                     SEL                                                                              BU       GDU PRM STK RT  STA                                     INBRED                                                                              PRM IND                                                                              ACR                                                                              YLD                                                                              MST                                                                              SHD SHD LDG LDG GRN                              __________________________________________________________________________    TOTAL  REPLIC.                                                                             109 126                                                                              131                                                                              131                                                                              131                                                                               21  16 85  52   64                              MEAN WTS                                                                             PHBG4 117  99                                                                              145                                                                              101                                                                              105                                                                              102 115 102 99  108                              MEAN WTS                                                                             PHR03 115 107                                                                              151                                                                              106                                                                              100                                                                              102 115 99  96  100                                     DIFF   2   8  7  4  5  1   0   3   3   7                               __________________________________________________________________________                  TST GRN  SDG EST STK                                                                              PLT EAR                                                                              DRP                                                                              BRT                                      INBRED WTA APP  VGR CNT CNT                                                                              HT  HT EAR                                                                              STK                               __________________________________________________________________________    TOTAL  REPLIC.                                                                               64 16   33   73 144                                                                              69  69  20                                                                               31                               MEAN WTS                                                                             PHBG4  102 99   104 100 100                                                                              97  95 100                                                                              102                               MEAN WTS                                                                             PHR03  102 102  98  102 101                                                                              101 99 100                                                                              105                                      DIFF    0   2    6   2   1  3   5  0  3                                __________________________________________________________________________

Deposits

Applicant has made a deposit of at least 2500 seeds of Inbred Corn LinePHBG4 with the American Type Culture Collection (ATCC), Rockville, Md.20852 USA, ATCC Deposit No. 97434. The seeds deposited with the ATCC onFeb. 8, 1996, were taken from the deposit maintained by Pioneer Hi-BredInternational, Inc., 700 Capital Square, 400 Locust Street, Des Moines,Iowa 50309-2340 since prior to the filing date of this application. Thisdeposit of the Inbred Corn Line PHBG4 will be maintained in the ATCCdepository, which is a public depository, for a period of 30 years, or 5years after the most recent request, or for the enforceable life of thepatent, whichever is longer, and will be replaced if it becomesnonviable during that period. Additionally, Applicant has satisfied allthe requirements of 37 C.F.R. §§1.801-1.809, including providing anindication of the viability of the sample. Applicant imposes norestrictions on the availability of the deposited material from theATCC; however, Applicant has no authority to waive any restrictionsimposed by law on the transfer of biological material or itstransportation in commerce. Applicant does not waive any infringement ofits rights granted under this patent or under the Plant VarietyProtection Act (7 USC 2321 et seq.). Applicant has applied for U.S.Plant Variety Protection of PHBG4 under Application No. 9500202.

The foregoing invention has been described in detail by way ofillustration and example for purposes of clarity and understanding.However, it will be obvious that certain changes and modifications suchas single gene modifications and mutations, somoclonal variants, variantindividuals selected from large populations of the plants of the instantinbred and the like may be practiced within the scope of the invention,as limited only by the scope of the appended claims.

What is claimed is:
 1. Seed of maize inbred line designated PHBG4 andhaving ATCC Accession No.
 97434. 2. A maize plant produced by the seedof claim 1 and its plant parts.
 3. Pollen of the plant of claim
 2. 4. Anovule of the plant of claim
 2. 5. A maize plant having all thephysiological and morphological characteristics of the plant of claim 2.6. A male sterile maize plant otherwise having all the physiological andmorphological characteristics of the plant of claim
 2. 7. A tissueculture of regenerable cells of an inbred maize plant PHBG4, wherein thetissue regenerates plants capable of expressing all the morphologicaland physiological characteristics of the maize plant named PHBG4, theseed of which have been deposited and have ATCC Accession No.
 97434. 8.A tissue culture of claim 7, the tissue culture selected from the groupconsisting of leaves, pollen, embryos, roots, root tips, anthers, silk,flowers, kernels, ears, cobs, husks, stalks, cells and protoplaststhereof.
 9. A maize plant regenerated from a tissue culture of claim 7,capable of expressing all the morphological and physiologicalcharacteristics of inbred PHBG4, the seed of which have been depositedunder ATCC Accession No.
 97434. 10. A method for producing firstgeneration (F₁) hybrid maize seed, which gives rise to a hybrid maizeplant having alleles that, when expressed, contribute to hybrids thatare high yielding and have very good stay green, comprising crossing theplant of claim 2 with a different inbred parent maize plant andharvesting the resultant first generation (F₁ ) hybrid maize seed. 11.The method of claim 10 wherein inbred maize plant PHBG4 is the femaleparent.
 12. The method of claim 10 wherein inbred maize plant PHBG4 isthe male parent.
 13. An F₁ hybrid seed and plant, and its parts, growntherefrom produced by crossing an inbred maize plant according to claim2 with another, different maize plant.